HOUSTON — Across hot, humid Harris County, mosquitoes are trapped and hauled to a facility south of downtown here. After being dunked into a freezer and sorted, the females — the ones that bite — are crushed, sampled, and tested for signs of disease like dengue and West Nile.

These days, scientists at the county’s mosquito control headquarters have added another threat to their watch list: the Zika virus.

Harris County is home to year-round populations of the primary driver of the ongoing Zika outbreak in the Americas, Aedes aegypti mosquitoes. Like the rest of the continental United States, the county, which at 1,700 square miles is larger than Rhode Island, has not seen any local Zika cases spread by mosquitoes.

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But many public health officials say it might only be a matter of time before this area sees such cases. Other cases could appear across Texas, and in Florida and Hawaii, as mosquitoes enter their peak reproductive season in the coming months. (There have been 12 cases of travel-related Zika in Harris County so far, including in Houston.)

In many ways, Harris County is better prepared than other places. Its mosquito control program dates back more than 50 years, and with an approximate annual budget of $4 million, it is among the best funded divisions in the country. While mosquito control in other places falls to crews who also fill in potholes or plow roads, the facility here has a virology lab that is upgrading its equipment to be able to distinguish Zika from related viruses based on its genetic information.

CDC

During the mosquito low season, the virology team will test up to 100 vials filled with as many as 50 mosquitoes each week. During the peak season, they will test up to 600 vials. And if they find virus in any mosquito sample, crews will ramp up their control efforts in the areas where those mosquitoes were found.

But even here, in one of the best equipped counties, officials face an uphill battle against the formidable mosquito, and in getting residents to aid their efforts. On a recent morning, a tower of three tires — prime breeding sites for Aedes mosquitoes — appeared just down the street from mosquito control headquarters.

As Mustapha Debboun, director of the mosquito control program, approached, a swarm of mosquitoes scattered. From one of the tires, Debboun collected a sample of water with a small white cup. Inside, a smattering of squiggling mosquito larvae were growing.

“You guys are not going to live,” Debboun said, dumping the cup in the grass.